Recently, as portable terminals have been drastically developed, portable terminals used especially for wireless voice calls and exchanges of information became necessities.
At the beginning of supplying of portable terminals, portable terminals are just recognized as portable tools just for wireless voice calls, but as their technologies are developed, and wireless Internet is introduced, the range of applications of portable terminals, such as games, watching of satellite broadcasting, remote controls using near field communications, imaging of built-in digital cameras, and schedule organizing as well as phone calls, is increased to satisfy users' demands.
Digital cameras form moving images of a moving subject as well as still images. Especially, portable imaging devices are widely used to photograph people.
When a portable terminal is used to photograph a person, a shutter should be accurately pressed just when a face is disposed on a screen. However, since positioning of a person is not easy, photographing a moving person can be difficult. To address this limitation, active research is recently being carried out on construction of a Human Computer Interaction (HCI) system for a facial expression recognition system and user recognition/adaptation. However, a face should be accurately detected to recognize expression, and accurate detection of a face from a still or moving image is difficult.
Faces having various sizes, beards, the presence of structures such as glasses, positions of faces, variations of illumination, characteristics of cameras, variations of facial expression make it difficult to detect faces. That is, a large number of training images for generating a detector model is necessary to perform the above functions, and a training process that requires a large number of processes to uniformly maintain positions of the training images is necessary.
Additionally, when angle variation is large in detecting a rotated face, detection processes at various angles should be repeated on a single input image.
The above limitations occur more frequently when detecting hand motions that have more position variations than those of facial regions.
Products having a function recognizing a hand motion in a portable terminal are recently commercialized, but improvement in the hand motion detection performance is required.